Valve assembly with pressure disturbance rejection and fault detection and diagnosis

ABSTRACT

A pressure disturbance rejection valve assembly is provided. The valve assembly includes a valve, a flow rate sensor, and an actuator. The actuator includes a motor, a drive device configured to be driven by the motor and coupled to the valve for driving the valve within a range of positions, and a position sensor configured to measure a rotational position of the drive device. The actuator further includes a communications mechanism configured to receive a flow rate setpoint and a processing circuit. The processing circuit is configured to determine an actuator position setpoint using a feedback control mechanism based on the flow rate setpoint and the flow rate measurement, operate the motor to drive the drive device to the actuator position setpoint, detect a fault condition based at least in part on the rotational position measurement or the flow rate measurement, and perform a fault mitigation action in response to detection of the fault condition.

BACKGROUND

The present disclosure relates generally to the field of buildingmanagement systems and associated devices and more particularly tosystems and methods for detecting and diagnosing faults in a pressuredisturbance rejection valve assembly. A pressure disturbance rejectionvalve assembly includes an onboard electronic controller that isagnostic to system pressure fluctuations and instead controls a valveposition based on a flow command received from an external controldevice and a flow rate measurement received from a flow rate sensor.

Like all electromechanical devices, pressure disturbance rejection valveassemblies may experience occasional faults due to the failure ofelectrical and/or mechanical components. In many cases, it is useful foradministrators of a building management system (BMS) in which the valveassembly is installed to be alerted to faults as soon as they occur, sothat they may be monitored or addressed as befits their severity. It istherefore advantageous to leverage the components of the pressuredisturbance rejection valve assembly to perform fault detectionfunctions.

SUMMARY

One implementation of the present disclosure is a pressure disturbancerejection valve assembly. The valve assembly includes a valve configuredto regulate a flow rate of a fluid through a conduit, a flow ratesensor, and an actuator. The flow rate sensor is configured to measurethe flow rate of the fluid through the conduit and provide a flow ratemeasurement indicating the flow rate of the fluid through the conduit.The actuator includes a motor, a drive device configured to be driven bythe motor and coupled to the valve for driving the valve within a rangeof positions, and a position sensor configured to measure a rotationalposition of the drive device and provide a rotational positionmeasurement indicating the rotational position of the drive device. Thevalve assembly further includes a communications mechanism configured toreceive a flow rate setpoint and a processing circuit. The processingcircuit is configured to determine an actuator position setpoint using afeedback control mechanism based on the flow rate setpoint and the flowrate measurement, operate the motor to drive the drive device to theactuator position setpoint, detect a fault condition based at least inpart on the rotational position measurement or the flow ratemeasurement, and perform a fault mitigation action in response todetection of the fault condition.

In some embodiments, the communications mechanism is configured toreceive the flow rate setpoint as an analog input signal or a digitalinput signal. In some embodiments, the feedback control mechanism is acascaded feedback control mechanism.

In some embodiments, the fault condition is a position fault. Theposition fault may include a difference between the actuator positionsetpoint and the rotational position measurement exceeding a positionerror value.

In some embodiments, the fault condition is a low flow fault. The lowflow fault may include the flow rate measurement being less than a flowrate setpoint value when the rotational position measurement indicatesthat the valve is in a fully open position. In further embodiments, thefault condition is a no flow fault. The no flow fault may include theflow rate measurement being less than a minimum rated flow rate valuewhen the rotational position measurement indicates that the valveexceeds a minimum open position. In still further embodiments, the faultcondition is a leaky valve fault. The leaky valve fault may include theflow rate measurement exceeding a leaky flow rate value when therotational position measurement indicates that the valve is in a fullyclosed position.

In some embodiments, the fault mitigation action includes at least oneof transmitting a fault notification message, activating a system alarm,logging an entry in a system log, illuminating a fault indicator light,and operating in a fault tolerant control mode.

Another implementation of the present disclosure is a method forcontrolling a pressure disturbance rejection valve assembly in an HVACsystem. The method includes determining an actuator position setpoint ofan actuator based on a flow rate setpoint and a flow rate measurement,and driving the actuator to the actuator position setpoint. The actuatoris coupled to a valve in order to drive the valve within a range ofpositions. The method further includes measuring a flow rate of fluidthrough the valve, detecting a fault condition based at least in part ona rotational position measurement of the actuator or a flow ratemeasurement, and performing a fault mitigation action in response todetection of the fault condition.

In some embodiments, the fault condition is a position fault. Theposition fault may include a difference between the actuator positionsetpoint and the rotational position measurement exceeding a positionerror value.

In some embodiments, the fault condition is a low flow fault. The lowflow fault may include the flow rate measurement being less than a flowrate setpoint value when the rotational position measurement indicatesthat the valve is in a fully open position. In further embodiments, thefault condition is a no flow fault. The no flow fault may include theflow rate measurement being less than a minimum rated flow rate valuewhen the rotational position measurement indicates that the valveexceeds a minimum open position. In still further embodiments, the faultcondition is a leaky valve fault. The leaky valve fault may include theflow rate measurement exceeding a leaky flow rate value when therotational position measurement indicates that the valve is in a fullyclosed position.

Yet another implementation of the present disclosure is an actuator. Theactuator includes a motor, a drive device configured to be driven by themotor, and a position sensor configured to measure a rotational positionof the drive device and provide a rotational position measurementindicating the rotational position of the drive device. The actuatorfurther includes a communications mechanism configured to receive a flowrate setpoint and a processing circuit. The processing circuit isconfigured to determine an actuator position setpoint using a feedbackcontrol mechanism based on the flow rate setpoint and a flow ratemeasurement from a flow sensor, operate the motor to drive the drivedevice to the actuator position setpoint, detect a fault condition basedat least in part on the rotational position measurement or the flow ratemeasurement, and perform a fault mitigation action in response todetection of the fault condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing of a building equipped with a heating, ventilating,or air conditioning (HVAC) system and a building management system(BMS), according to some embodiments.

FIG. 2 is a schematic diagram of a waterside system that can be used tosupport the HVAC system of FIG. 1, according to some embodiments.

FIG. 3 is a block diagram of an airside system that can be used as partof the HVAC system of FIG. 1, according to some embodiments.

FIG. 4 is a block diagram of a BMS that can be implemented in thebuilding of FIG. 1, according to some embodiments.

FIG. 5 is a block diagram of a pressure disturbance rejection valveassembly that can be implemented in the HVAC system of FIG. 1, accordingto some embodiments.

FIG. 6 is a block diagram of another pressure disturbance rejectionvalve assembly that can be implemented in the HVAC system of FIG. 1,according to some embodiments.

FIG. 7 is a block diagram of a pressure disturbance rejection valveassembly within a feedback control system that can be implemented in theHVAC system of FIG. 1, according to some embodiments.

FIG. 8 is a state transition diagram illustrating the state transitionsand transition conditions experienced by a pressure disturbancerejection valve assembly during a valve position fault condition,according to some embodiments.

FIG. 9 is a state transition diagram illustrating the state transitionsand transition conditions experienced by a pressure disturbancerejection valve assembly during a low flow fault condition, according tosome embodiments.

FIG. 10 is a state transition diagram illustrating the state transitionsand transition conditions experienced by a pressure disturbancerejection valve assembly during a no flow fault condition, according tosome embodiments.

FIG. 11 is a state transition diagram illustrating the state transitionsand transition conditions experienced by a pressure disturbancerejection valve assembly during a leaky valve condition, according tosome embodiments.

FIG. 12 is a flowchart of a process for operating a pressure disturbancerejection valve assembly, according to some embodiments.

DETAILED DESCRIPTION Overview

Before turning to the FIGURES, which illustrate the exemplaryembodiments in detail, it should be understood that the disclosure isnot limited to the details or methodology set forth in the descriptionor illustrated in the figures. It should also be understood that theterminology is for the purpose of description only and should not beregarded as limiting.

Referring generally to the FIGURES, various systems and methods fordetecting and diagnosing faults in a pressure disturbance rejectionvalve assembly are shown, according to some embodiments. The pressuredisturbance rejection valve assembly includes, at minimum, anelectronically-controlled actuator, a valve, and a flow sensor. Theactuator may include an input/output (I/O) component circuit cardassembly (CCA), a control component CCA, and a hardware component CCA.In operation, the I/O component CCA receives a flow command (e.g.,0%-100%) from an external source (e.g., another controller, a buildingmanagement system (BMS)) and measured flow readings from a flow sensor.The I/O component CCA then communicates this data to the controlcomponent CCA, which utilizes a control technique (e.g., proportionalvariable deadband control (PVDC)) to determine an actuator and valveposition setpoint. The control component CCA transmits the positionsetpoint to the hardware component CCA, which rotates a valve stem ofthe valve to reach the setpoint. The control component CCA constantlymonitors the measured flow and the flow setpoint, and adjusts the valveposition accordingly in order to minimize the error between the measuredflow and the flow setpoint.

Faults that may occur in a pressure disturbance rejection valve assemblyinclude, but are not limited to, sensor-related faults, valve-relatedfaults, and system-related faults. Sensor-related faults may occur whena sensor is not properly calibrated, when a sensor with moving parts isjammed, or when sensor components (e.g., sensor wiring) are damaged.Valve-related faults may occur when a valve member is jammed or whenflow through the valve is non-zero when the valve member is ostensiblyin a full shutoff position (i.e., a leaky valve). System-related faultsmay include incorrect system parameter or component configurations(e.g., closed isolation valves), unstable control techniques, anddamaged or malfunctioning system components (e.g., pumps that do notprovide rated pressure values).

The embodiments of the pressure disturbance rejection valve assemblydisclosed herein are configured to detect the faults described above andperform fault mitigation actions in response to the detection of faults.Fault mitigation actions may vary based on the severity of the fault andthe system environment in which the pressure disturbance rejection valveassembly is installed. For example, in some systems, the faultmitigation action may include transmitting a fault notification messageto an administrator, activating an alarm, or illuminating an indicatorlight. In some cases, a supervisory device might assume control of thevalve from the actuator to enable a fault tolerant control scheme.

Building Management System and HVAC System

Referring now to FIGS. 1-4, an exemplary BMS and HVAC system in whichthe systems and methods of the present disclosure can be implemented areshown, according to some embodiments. Referring particularly to FIG. 1,a perspective view of a building 10 is shown. Building 10 is served by aBMS. A BMS is, in general, a system of devices configured to control,monitor, and manage equipment in or around a building or building area.A BMS can include, for example, a HVAC system, a security system, alighting system, a fire alerting system, any other system that iscapable of managing building functions or devices, or any combinationthereof.

The BMS that serves building 10 includes an HVAC system 100. HVAC system100 may include a plurality of HVAC devices (e.g., heaters, chillers,air handling units, pumps, fans, thermal energy storage, etc.)configured to provide heating, cooling, ventilation, or other servicesfor building 10. For example, HVAC system 100 is shown to include awaterside system 120 and an airside system 130. Waterside system 120 mayprovide a heated or chilled fluid to an air handling unit of airsidesystem 130. Airside system 130 may use the heated or chilled fluid toheat or cool an airflow provided to building 10. An exemplary watersidesystem and airside system which can be used in HVAC system 100 aredescribed in greater detail with reference to FIGS. 2-3.

HVAC system 100 is shown to include a chiller 102, a boiler 104, and arooftop air handling unit (AHU) 106. Waterside system 120 may use boiler104 and chiller 102 to heat or cool a working fluid (e.g., water,glycol, etc.) and may circulate the working fluid to AHU 106. In variousembodiments, the HVAC devices of waterside system 120 can be located inor around building 10 (as shown in FIG. 1) or at an offsite locationsuch as a central plant (e.g., a chiller plant, a steam plant, a heatplant, etc.). The working fluid can be heated in boiler 104 or cooled inchiller 102, depending on whether heating or cooling is required inbuilding 10. Boiler 104 may add heat to the circulated fluid, forexample, by burning a combustible material (e.g., natural gas) or usingan electric heating element. Chiller 102 may place the circulated fluidin a heat exchange relationship with another fluid (e.g., a refrigerant)in a heat exchanger (e.g., an evaporator) to absorb heat from thecirculated fluid. The working fluid from chiller 102 and/or boiler 104can be transported to AHU 106 via piping 108.

AHU 106 may place the working fluid in a heat exchange relationship withan airflow passing through AHU 106 (e.g., via one or more stages ofcooling coils and/or heating coils). The airflow can be, for example,outside air, return air from within building 10, or a combination ofboth. AHU 106 may transfer heat between the airflow and the workingfluid to provide heating or cooling for the airflow. For example, AHU106 may include one or more fans or blowers configured to pass theairflow over or through a heat exchanger containing the working fluid.The working fluid may then return to chiller 102 or boiler 104 viapiping 110.

Airside system 130 may deliver the airflow supplied by AHU 106 (i.e.,the supply airflow) to building 10 via air supply ducts 112 and mayprovide return air from building 10 to AHU 106 via air return ducts 114.In some embodiments, airside system 130 includes multiple variable airvolume (VAV) units 116. For example, airside system 130 is shown toinclude a separate VAV unit 116 on each floor or zone of building 10.VAV units 116 may include dampers or other flow control elements thatcan be operated to control an amount of the supply airflow provided toindividual zones of building 10. In other embodiments, airside system130 delivers the supply airflow into one or more zones of building 10(e.g., via supply ducts 112) without using intermediate VAV units 116 orother flow control elements. AHU 106 may include various sensors (e.g.,temperature sensors, pressure sensors, etc.) configured to measureattributes of the supply airflow. AHU 106 may receive input from sensorslocated within AHU 106 and/or within the building zone and may adjustthe flow rate, temperature, or other attributes of the supply airflowthrough AHU 106 to achieve setpoint conditions for the building zone.

Referring now to FIG. 2, a block diagram of a waterside system 200 isshown, according to some embodiments. In various embodiments, watersidesystem 200 may supplement or replace waterside system 120 in HVAC system100 or can be implemented separate from HVAC system 100. Whenimplemented in HVAC system 100, waterside system 200 may include asubset of the HVAC devices in HVAC system 100 (e.g., boiler 104, chiller102, pumps, valves, etc.) and may operate to supply a heated or chilledfluid to AHU 106. The HVAC devices of waterside system 200 can belocated within building 10 (e.g., as components of waterside system 120)or at an offsite location such as a central plant.

In FIG. 2, waterside system 200 is shown as a central plant having aplurality of subplants 202-212. Subplants 202-212 are shown to include aheater subplant 202, a heat recovery chiller subplant 204, a chillersubplant 206, a cooling tower subplant 208, a hot thermal energy storage(TES) subplant 210, and a cold thermal energy storage (TES) subplant212. Subplants 202-212 consume resources (e.g., water, natural gas,electricity, etc.) from utilities to serve the thermal energy loads(e.g., hot water, cold water, heating, cooling, etc.) of a building orcampus. For example, heater subplant 202 can be configured to heat waterin a hot water loop 214 that circulates the hot water between heatersubplant 202 and building 10. Chiller subplant 206 can be configured tochill water in a cold water loop 216 that circulates the cold waterbetween chiller subplant 206 building 10. Heat recovery chiller subplant204 can be configured to transfer heat from cold water loop 216 to hotwater loop 214 to provide additional heating for the hot water andadditional cooling for the cold water. Condenser water loop 218 mayabsorb heat from the cold water in chiller subplant 206 and reject theabsorbed heat in cooling tower subplant 208 or transfer the absorbedheat to hot water loop 214. Hot TES subplant 210 and cold TES subplant212 may store hot and cold thermal energy, respectively, for subsequentuse.

Hot water loop 214 and cold water loop 216 may deliver the heated and/orchilled water to air handlers located on the rooftop of building 10(e.g., AHU 106) or to individual floors or zones of building 10 (e.g.,VAV units 116). The air handlers push air past heat exchangers (e.g.,heating coils or cooling coils) through which the water flows to provideheating or cooling for the air. The heated or cooled air can bedelivered to individual zones of building 10 to serve the thermal energyloads of building 10. The water then returns to subplants 202-212 toreceive further heating or cooling.

Although subplants 202-212 are shown and described as heating andcooling water for circulation to a building, it is understood that anyother type of working fluid (e.g., glycol, CO2, etc.) can be used inplace of or in addition to water to serve the thermal energy loads. Inother embodiments, subplants 202-212 may provide heating and/or coolingdirectly to the building or campus without requiring an intermediateheat transfer fluid. These and other variations to waterside system 200are within the teachings of the present disclosure.

Each of subplants 202-212 may include a variety of equipment configuredto facilitate the functions of the subplant. For example, heatersubplant 202 is shown to include a plurality of heating elements 220(e.g., boilers, electric heaters, etc.) configured to add heat to thehot water in hot water loop 214. Heater subplant 202 is also shown toinclude several pumps 222 and 224 configured to circulate the hot waterin hot water loop 214 and to control the flow rate of the hot waterthrough individual heating elements 220. Chiller subplant 206 is shownto include a plurality of chillers 232 configured to remove heat fromthe cold water in cold water loop 216. Chiller subplant 206 is alsoshown to include several pumps 234 and 236 configured to circulate thecold water in cold water loop 216 and to control the flow rate of thecold water through individual chillers 232.

Heat recovery chiller subplant 204 is shown to include a plurality ofheat recovery heat exchangers 226 (e.g., refrigeration circuits)configured to transfer heat from cold water loop 216 to hot water loop214. Heat recovery chiller subplant 204 is also shown to include severalpumps 228 and 230 configured to circulate the hot water and/or coldwater through heat recovery heat exchangers 226 and to control the flowrate of the water through individual heat recovery heat exchangers 226.Cooling tower subplant 208 is shown to include a plurality of coolingtowers 238 configured to remove heat from the condenser water incondenser water loop 218. Cooling tower subplant 208 is also shown toinclude several pumps 240 configured to circulate the condenser water incondenser water loop 218 and to control the flow rate of the condenserwater through individual cooling towers 238.

Hot TES subplant 210 is shown to include a hot TES tank 242 configuredto store the hot water for later use. Hot TES subplant 210 may alsoinclude one or more pumps or valves configured to control the flow rateof the hot water into or out of hot TES tank 242. Cold TES subplant 212is shown to include cold TES tanks 244 configured to store the coldwater for later use. Cold TES subplant 212 may also include one or morepumps or valves configured to control the flow rate of the cold waterinto or out of cold TES tanks 244.

In some embodiments, one or more of the pumps in waterside system 200(e.g., pumps 222, 224, 228, 230, 234, 236, and/or 240) or pipelines inwaterside system 200 include an isolation valve associated therewith.Isolation valves can be integrated with the pumps or positioned upstreamor downstream of the pumps to control the fluid flows in watersidesystem 200. In various embodiments, waterside system 200 may includemore, fewer, or different types of devices and/or subplants based on theparticular configuration of waterside system 200 and the types of loadsserved by waterside system 200.

Referring now to FIG. 3, a block diagram of an airside system 300 isshown, according to some embodiments. In various embodiments, airsidesystem 300 may supplement or replace airside system 130 in HVAC system100 or can be implemented separate from HVAC system 100. Whenimplemented in HVAC system 100, airside system 300 may include a subsetof the HVAC devices in HVAC system 100 (e.g., AHU 106, VAV units 116,ducts 112-114, fans, dampers, etc.) and can be located in or aroundbuilding 10. Airside system 300 may operate to heat or cool an airflowprovided to building 10 using a heated or chilled fluid provided bywaterside system 200.

In FIG. 3, airside system 300 is shown to include an economizer-type airhandling unit (AHU) 302. Economizer-type AHUs vary the amount of outsideair and return air used by the air handling unit for heating or cooling.For example, AHU 302 may receive return air 304 from building zone 306via return air duct 308 and may deliver supply air 310 to building zone306 via supply air duct 312. In some embodiments, AHU 302 is a rooftopunit located on the roof of building 10 (e.g., AHU 106 as shown inFIG. 1) or otherwise positioned to receive both return air 304 andoutside air 314. AHU 302 can be configured to operate exhaust air damper316, mixing damper 318, and outside air damper 320 to control an amountof outside air 314 and return air 304 that combine to form supply air310. Any return air 304 that does not pass through mixing damper 318 canbe exhausted from AHU 302 through exhaust damper 316 as exhaust air 322.

Each of dampers 316-320 can be operated by an actuator. For example,exhaust air damper 316 can be operated by actuator 324, mixing damper318 can be operated by actuator 326, and outside air damper 320 can beoperated by actuator 328. Actuators 324-328 may communicate with an AHUcontroller 330 via a communications link 332. Actuators 324-328 mayreceive control signals from AHU controller 330 and may provide feedbacksignals to AHU controller 330. Feedback signals may include, forexample, an indication of a current actuator or damper position, anamount of torque or force exerted by the actuator, diagnosticinformation (e.g., results of diagnostic tests performed by actuators324-328), status information, commissioning information, configurationsettings, calibration data, and/or other types of information or datathat can be collected, stored, or used by actuators 324-328. AHUcontroller 330 can be an economizer controller configured to use one ormore control algorithms (e.g., state-based algorithms, extremum seekingcontrol (ESC) algorithms, proportional-integral (PI) control algorithms,proportional-integral-derivative (PID) control algorithms, modelpredictive control (MPC) algorithms, feedback control algorithms, etc.)to control actuators 324-328.

Still referring to FIG. 3, AHU 302 is shown to include a cooling coil334, a heating coil 336, and a fan 338 positioned within supply air duct312. Fan 338 can be configured to force supply air 310 through coolingcoil 334 and/or heating coil 336 and provide supply air 310 to buildingzone 306. AHU controller 330 may communicate with fan 338 viacommunications link 340 to control a flow rate of supply air 310. Insome embodiments, AHU controller 330 controls an amount of heating orcooling applied to supply air 310 by modulating a speed of fan 338.

Cooling coil 334 may receive a chilled fluid from waterside system 200(e.g., from cold water loop 216) via piping 342 and may return thechilled fluid to waterside system 200 via piping 344. Valve 346 can bepositioned along piping 342 or piping 344 to control a flow rate of thechilled fluid through cooling coil 334. In some embodiments, coolingcoil 334 includes multiple stages of cooling coils that can beindependently activated and deactivated (e.g., by AHU controller 330, byBMS controller 366, etc.) to modulate an amount of cooling applied tosupply air 310.

Heating coil 336 may receive a heated fluid from waterside system 200(e.g., from hot water loop 214) via piping 348 and may return the heatedfluid to waterside system 200 via piping 350. Valve 352 can bepositioned along piping 348 or piping 350 to control a flow rate of theheated fluid through heating coil 336. In some embodiments, heating coil336 includes multiple stages of heating coils that can be independentlyactivated and deactivated (e.g., by AHU controller 330, by BMScontroller 366, etc.) to modulate an amount of heating applied to supplyair 310.

Each of valves 346 and 352 can be controlled by an actuator. Forexample, valve 346 can be controlled by actuator 354 and valve 352 canbe controlled by actuator 356. Actuators 354-356 may communicate withAHU controller 330 via communications links 358-360. Actuators 354-356may receive control signals from AHU controller 330 and may providefeedback signals to controller 330. In some embodiments, AHU controller330 receives a measurement of the supply air temperature from atemperature sensor 362 positioned in supply air duct 312 (e.g.,downstream of cooling coil 334 and/or heating coil 336). AHU controller330 may also receive a measurement of the temperature of building zone306 from a temperature sensor 364 located in building zone 306.

In some embodiments, AHU controller 330 operates valves 346 and 352 viaactuators 354-356 to modulate an amount of heating or cooling providedto supply air 310 (e.g., to achieve a setpoint temperature for supplyair 310 or to maintain the temperature of supply air 310 within asetpoint temperature range). The positions of valves 346 and 352 affectthe amount of heating or cooling provided to supply air 310 by coolingcoil 334 or heating coil 336 and may correlate with the amount of energyconsumed to achieve a desired supply air temperature. AHU controller 330may control the temperature of supply air 310 and/or building zone 306by activating or deactivating coils 334-336, adjusting a speed of fan338, or a combination of both.

Still referring to FIG. 3, airside system 300 is shown to include abuilding management system (BMS) controller 366 and a client device 368.BMS controller 366 may include one or more computer systems (e.g.,servers, supervisory controllers, subsystem controllers, etc.) thatserve as system level controllers, application or data servers, headnodes, or master controllers for airside system 300, waterside system200, HVAC system 100, and/or other controllable systems that servebuilding 10. BMS controller 366 may communicate with multiple downstreambuilding systems or subsystems (e.g., HVAC system 100, a securitysystem, a lighting system, waterside system 200, etc.) via acommunications link 370 according to like or disparate protocols (e.g.,LON, BACnet, etc.). In various embodiments, AHU controller 330 and BMScontroller 366 can be separate (as shown in FIG. 3) or integrated. In anintegrated implementation, AHU controller 330 can be a software moduleconfigured for execution by a processor of BMS controller 366.

In some embodiments, AHU controller 330 receives information from BMScontroller 366 (e.g., commands, setpoints, operating boundaries, etc.)and provides information to BMS controller 366 (e.g., temperaturemeasurements, valve or actuator positions, operating statuses,diagnostics, etc.). For example, AHU controller 330 may provide BMScontroller 366 with temperature measurements from temperature sensors362-364, equipment on/off states, equipment operating capacities, and/orany other information that can be used by BMS controller 366 to monitoror control a variable state or condition within building zone 306.

Client device 368 may include one or more human-machine interfaces orclient interfaces (e.g., graphical user interfaces, reportinginterfaces, text-based computer interfaces, client-facing web services,web servers that provide pages to web clients, etc.) for controlling,viewing, or otherwise interacting with HVAC system 100, its subsystems,and/or devices. Client device 368 can be a computer workstation, aclient terminal, a remote or local interface, or any other type of userinterface device. Client device 368 can be a stationary terminal or amobile device. For example, client device 368 can be a desktop computer,a computer server with a user interface, a laptop computer, a tablet, asmartphone, a PDA, or any other type of mobile or non-mobile device.Client device 368 may communicate with BMS controller 366 and/or AHUcontroller 330 via communications link 372.

Referring now to FIG. 4, a block diagram of a building management system(BMS) 400 is shown, according to some embodiments. BMS 400 can beimplemented in building 10 to automatically monitor and control variousbuilding functions. BMS 400 is shown to include BMS controller 366 and aplurality of building subsystems 428. Building subsystems 428 are shownto include a building electrical subsystem 434, an informationcommunication technology (ICT) subsystem 436, a security subsystem 438,a HVAC subsystem 440, a lighting subsystem 442, a lift/escalatorssubsystem 432, and a fire safety subsystem 430. In various embodiments,building subsystems 428 can include fewer, additional, or alternativesubsystems. For example, building subsystems 428 may also oralternatively include a refrigeration subsystem, an advertising orsignage subsystem, a cooking subsystem, a vending subsystem, a printeror copy service subsystem, or any other type of building subsystem thatuses controllable equipment and/or sensors to monitor or controlbuilding 10. In some embodiments, building subsystems 428 includewaterside system 200 and/or airside system 300, as described withreference to FIGS. 2-3.

Each of building subsystems 428 may include any number of devices,controllers, and connections for completing its individual functions andcontrol activities. HVAC subsystem 440 may include many of the samecomponents as HVAC system 100, as described with reference to FIGS. 1-3.For example, HVAC subsystem 440 may include and number of chillers,heaters, handling units, economizers, field controllers, supervisorycontrollers, actuators, temperature sensors, and/or other devices forcontrolling the temperature, humidity, airflow, or other variableconditions within building 10. Lighting subsystem 442 may include anynumber of light fixtures, ballasts, lighting sensors, dimmers, or otherdevices configured to controllably adjust the amount of light providedto a building space. Security subsystem 438 may include occupancysensors, video surveillance cameras, digital video recorders, videoprocessing servers, intrusion detection devices, access control devicesand servers, or other security-related devices.

Still referring to FIG. 4, BMS controller 366 is shown to include acommunications interface 407 and a BMS interface 409. Interface 407 mayfacilitate communications between BMS controller 366 and externalapplications (e.g., monitoring and reporting applications 422,enterprise control applications 426, remote systems and applications444, applications residing on client devices 448, etc.) for allowinguser control, monitoring, and adjustment to BMS controller 366 and/orsubsystems 428. Interface 407 may also facilitate communications betweenBMS controller 366 and client devices 448. BMS interface 409 mayfacilitate communications between BMS controller 366 and buildingsubsystems 428 (e.g., HVAC, lighting security, lifts, powerdistribution, business, etc.).

Interfaces 407, 409 can be or include wired or wireless communicationsinterfaces (e.g., jacks, antennas, transmitters, receivers,transceivers, wire terminals, etc.) for conducting data communicationswith building subsystems 428 or other external systems or devices. Invarious embodiments, communications via interfaces 407, 409 can bedirect (e.g., local wired or wireless communications) or via acommunications network 446 (e.g., a WAN, the Internet, a cellularnetwork, etc.). For example, interfaces 407, 409 can include an Ethernetcard and port for sending and receiving data via an Ethernet-basedcommunications link or network. In another example, interfaces 407, 409can include a WiFi transceiver for communicating via a wirelesscommunications network. In another example, one or both of interfaces407, 409 may include cellular or mobile phone communicationstransceivers. In one embodiment, communications interface 407 is a powerline communications interface and BMS interface 409 is an Ethernetinterface. In other embodiments, both communications interface 407 andBMS interface 409 are Ethernet interfaces or are the same Ethernetinterface.

Still referring to FIG. 4, BMS controller 366 is shown to include aprocessing circuit 404 including a processor 406 and memory 408.Processing circuit 404 can be communicably connected to BMS interface409 and/or communications interface 407 such that processing circuit 404and the various components thereof can send and receive data viainterfaces 407, 409. Processor 406 can be implemented as a generalpurpose processor, an application specific integrated circuit (ASIC),one or more field programmable gate arrays (FPGAs), a group ofprocessing components, or other suitable electronic processingcomponents.

Memory 408 (e.g., memory, memory unit, storage device, etc.) may includeone or more devices (e.g., RAM, ROM, Flash memory, hard disk storage,etc.) for storing data and/or computer code for completing orfacilitating the various processes, layers and modules described in thepresent application. Memory 408 can be or include volatile memory ornon-volatile memory. Memory 408 may include database components, objectcode components, script components, or any other type of informationstructure for supporting the various activities and informationstructures described in the present application. According to someembodiments, memory 408 is communicably connected to processor 406 viaprocessing circuit 404 and includes computer code for executing (e.g.,by processing circuit 404 and/or processor 406) one or more processesdescribed herein.

In some embodiments, BMS controller 366 is implemented within a singlecomputer (e.g., one server, one housing, etc.). In various otherembodiments BMS controller 366 can be distributed across multipleservers or computers (e.g., that can exist in distributed locations).Further, while FIG. 4 shows applications 422 and 426 as existing outsideof BMS controller 366, in some embodiments, applications 422 and 426 canbe hosted within BMS controller 366 (e.g., within memory 408).

Still referring to FIG. 4, memory 408 is shown to include an enterpriseintegration layer 410, an automated measurement and validation (AM&V)layer 412, a demand response (DR) layer 414, a fault detection anddiagnostics (FDD) layer 416, an integrated control layer 418, and abuilding subsystem integration later 420. Layers 410-420 can beconfigured to receive inputs from building subsystems 428 and other datasources, determine optimal control actions for building subsystems 428based on the inputs, generate control signals based on the optimalcontrol actions, and provide the generated control signals to buildingsubsystems 428. The following paragraphs describe some of the generalfunctions performed by each of layers 410-420 in BMS 400.

Enterprise integration layer 410 can be configured to serve clients orlocal applications with information and services to support a variety ofenterprise-level applications. For example, enterprise controlapplications 426 can be configured to provide subsystem-spanning controlto a graphical user interface (GUI) or to any number of enterprise-levelbusiness applications (e.g., accounting systems, user identificationsystems, etc.). Enterprise control applications 426 may also oralternatively be configured to provide configuration GUIs forconfiguring BMS controller 366. In yet other embodiments, enterprisecontrol applications 426 can work with layers 410-420 to optimizebuilding performance (e.g., efficiency, energy use, comfort, or safety)based on inputs received at interface 407 and/or BMS interface 409.

Building subsystem integration layer 420 can be configured to managecommunications between BMS controller 366 and building subsystems 428.For example, building subsystem integration layer 420 may receive sensordata and input signals from building subsystems 428 and provide outputdata and control signals to building subsystems 428. Building subsystemintegration layer 420 may also be configured to manage communicationsbetween building subsystems 428. Building subsystem integration layer420 translate communications (e.g., sensor data, input signals, outputsignals, etc.) across a plurality of multi-vendor/multi-protocolsystems.

Demand response layer 414 can be configured to optimize resource usage(e.g., electricity use, natural gas use, water use, etc.) and/or themonetary cost of such resource usage in response to satisfy the demandof building 10. The optimization can be based on time-of-use prices,curtailment signals, energy availability, or other data received fromutility providers, distributed energy generation systems 424, fromenergy storage 427 (e.g., hot TES 242, cold TES 244, etc.), or fromother sources. Demand response layer 414 may receive inputs from otherlayers of BMS controller 366 (e.g., building subsystem integration layer420, integrated control layer 418, etc.). The inputs received from otherlayers may include environmental or sensor inputs such as temperature,carbon dioxide levels, relative humidity levels, air quality sensoroutputs, occupancy sensor outputs, room schedules, and the like. Theinputs may also include inputs such as electrical use (e.g., expressedin kWh), thermal load measurements, pricing information, projectedpricing, smoothed pricing, curtailment signals from utilities, and thelike.

According to some embodiments, demand response layer 414 includescontrol logic for responding to the data and signals it receives. Theseresponses can include communicating with the control algorithms inintegrated control layer 418, changing control strategies, changingsetpoints, or activating/deactivating building equipment or subsystemsin a controlled manner. Demand response layer 414 may also includecontrol logic configured to determine when to utilize stored energy. Forexample, demand response layer 414 may determine to begin using energyfrom energy storage 427 just prior to the beginning of a peak use hour.

In some embodiments, demand response layer 414 includes a control moduleconfigured to actively initiate control actions (e.g., automaticallychanging setpoints) which minimize energy costs based on one or moreinputs representative of or based on demand (e.g., price, a curtailmentsignal, a demand level, etc.). In some embodiments, demand responselayer 414 uses equipment models to determine an optimal set of controlactions. The equipment models may include, for example, thermodynamicmodels describing the inputs, outputs, and/or functions performed byvarious sets of building equipment. Equipment models may representcollections of building equipment (e.g., subplants, chiller arrays,etc.) or individual devices (e.g., individual chillers, heaters, pumps,etc.).

Demand response layer 414 may further include or draw upon one or moredemand response policy definitions (e.g., databases, XML files, etc.).The policy definitions can be edited or adjusted by a user (e.g., via agraphical user interface) so that the control actions initiated inresponse to demand inputs can be tailored for the user's application,desired comfort level, particular building equipment, or based on otherconcerns. For example, the demand response policy definitions canspecify which equipment can be turned on or off in response toparticular demand inputs, how long a system or piece of equipment shouldbe turned off, what setpoints can be changed, what the allowable setpoint adjustment range is, how long to hold a high demand setpointbefore returning to a normally scheduled setpoint, how close to approachcapacity limits, which equipment modes to utilize, the energy transferrates (e.g., the maximum rate, an alarm rate, other rate boundaryinformation, etc.) into and out of energy storage devices (e.g., thermalstorage tanks, battery banks, etc.), and when to dispatch on-sitegeneration of energy (e.g., via fuel cells, a motor generator set,etc.).

Integrated control layer 418 can be configured to use the data input oroutput of building subsystem integration layer 420 and/or demandresponse later 414 to make control decisions. Due to the subsystemintegration provided by building subsystem integration layer 420,integrated control layer 418 can integrate control activities of thesubsystems 428 such that the subsystems 428 behave as a singleintegrated supersystem. In some embodiments, integrated control layer418 includes control logic that uses inputs and outputs from a pluralityof building subsystems to provide greater comfort and energy savingsrelative to the comfort and energy savings that separate subsystemscould provide alone. For example, integrated control layer 418 can beconfigured to use an input from a first subsystem to make anenergy-saving control decision for a second subsystem. Results of thesedecisions can be communicated back to building subsystem integrationlayer 420.

Integrated control layer 418 is shown to be logically below demandresponse layer 414. Integrated control layer 418 can be configured toenhance the effectiveness of demand response layer 414 by enablingbuilding subsystems 428 and their respective control loops to becontrolled in coordination with demand response layer 414. Thisconfiguration may reduce disruptive demand response behavior relative toconventional systems. For example, integrated control layer 418 can beconfigured to assure that a demand response-driven upward adjustment tothe setpoint for chilled water temperature (or another component thatdirectly or indirectly affects temperature) does not result in anincrease in fan energy (or other energy used to cool a space) that wouldresult in greater total building energy use than was saved at thechiller.

Integrated control layer 418 can be configured to provide feedback todemand response layer 414 so that demand response layer 414 checks thatconstraints (e.g., temperature, lighting levels, etc.) are properlymaintained even while demanded load shedding is in progress. Theconstraints may also include setpoint or sensed boundaries relating tosafety, equipment operating limits and performance, comfort, fire codes,electrical codes, energy codes, and the like. Integrated control layer418 is also logically below fault detection and diagnostics layer 416and automated measurement and validation layer 412. Integrated controllayer 418 can be configured to provide calculated inputs (e.g.,aggregations) to these higher levels based on outputs from more than onebuilding subsystem.

Automated measurement and validation (AM&V) layer 412 can be configuredto verify that control strategies commanded by integrated control layer418 or demand response layer 414 are working properly (e.g., using dataaggregated by AM&V layer 412, integrated control layer 418, buildingsubsystem integration layer 420, FDD layer 416, or otherwise). Thecalculations made by AM&V layer 412 can be based on building systemenergy models and/or equipment models for individual BMS devices orsubsystems. For example, AM&V layer 412 may compare a model-predictedoutput with an actual output from building subsystems 428 to determinean accuracy of the model.

Fault detection and diagnostics (FDD) layer 416 can be configured toprovide on-going fault detection for building subsystems 428, buildingsubsystem devices (i.e., building equipment), and control algorithmsused by demand response layer 414 and integrated control layer 418. FDDlayer 416 may receive data inputs from integrated control layer 418,directly from one or more building subsystems or devices, or fromanother data source. FDD layer 416 may automatically diagnose andrespond to detected faults. The responses to detected or diagnosedfaults may include providing an alert message to a user, a maintenancescheduling system, or a control algorithm configured to attempt torepair the fault or to work—around the fault.

FDD layer 416 can be configured to output a specific identification ofthe faulty component or cause of the fault (e.g., loose damper linkage)using detailed subsystem inputs available at building subsystemintegration layer 420. In other exemplary embodiments, FDD layer 416 isconfigured to provide “fault” events to integrated control layer 418which executes control strategies and policies in response to thereceived fault events. According to some embodiments, FDD layer 416 (ora policy executed by an integrated control engine or business rulesengine) may shut-down systems or direct control activities around faultydevices or systems to reduce energy waste, extend equipment life, orassure proper control response.

FDD layer 416 can be configured to store or access a variety ofdifferent system data stores (or data points for live data). FDD layer416 may use some content of the data stores to identify faults at theequipment level (e.g., specific chiller, specific AHU, specific terminalunit, etc.) and other content to identify faults at component orsubsystem levels. For example, building subsystems 428 may generatetemporal (i.e., time-series) data indicating the performance of BMS 400and the various components thereof. The data generated by buildingsubsystems 428 may include measured or calculated values that exhibitstatistical characteristics and provide information about how thecorresponding system or process (e.g., a temperature control process, aflow control process, etc.) is performing in terms of error from itssetpoint. These processes can be examined by FDD layer 416 to exposewhen the system begins to degrade in performance and alert a user torepair the fault before it becomes more severe.

Pressure Disturbance Rejection Valve Assembly

Referring now to FIG. 5, a block diagram of a pressure disturbancerejection valve assembly 500 is shown, according to some embodiments.Valve assembly 500 may be used in HVAC system 100, waterside system 200,airside system 300, or BMS 400, as described with reference to FIGS.1-4. Valve assembly 500 is shown to include an actuator 502 coupled to avalve 504. For example, actuator 502 may be a damper actuator, a valveactuator, a fan actuator, a pump actuator, or any other type of actuatorthat can be used in an HVAC system or BMS. In various embodiments,actuator 502 may be a linear actuator (e.g., a linear proportionalactuator), a non-linear actuator, a spring return actuator, or anon-spring return actuator.

Valve 504 may be any type of control device configured to control anenvironmental parameter in an HVAC system, including a 2-way or 3-waytwo position electric motorized valve, a ball isolation valve, afloating point control valve, an adjustable flow control device, or amodulating control valve. In some embodiments, valve 504 may regulatethe flow of fluid through a conduit, pipe, or tube (e.g., conduit 512)in a waterside system (e.g., waterside system 200, shown in FIG. 2).Conduit 512 may include upstream conduit section 506 and downstreamconduit section 508. In other embodiments, valve 504 may regulate theflow of air through a duct in an airside system (e.g., airside system300, shown in FIG. 3).

In some embodiments, actuator 502 and valve 504 are located within acommon integrated device chassis or housing. In short, actuator 502 andvalve 504 may not be packaged as separate devices, but as a singledevice. Reducing the number of devices in an HVAC system may providenumerous advantages, most notably in time and cost savings during theinstallation process. Because it is not necessary to install actuator502 and valve 504 as separate devices and then make a connection betweenthem, technicians performing the installation may require lessspecialized training and fewer tools. Other advantages of a singledevice may include simplification of control and troubleshootingfunctions. However, in some embodiments, actuator 502 and valve 504 arepackaged as separate devices that may be communicably coupled via awired or a wireless connection.

Still referring to FIG. 5, flow sensor 510 is shown to be disposedwithin downstream conduit section 508. Flow sensor 510 may be configuredto measure the flow rate or velocity of fluid passing through conduit512, and more specifically, the flow rate of fluid exiting valve 504.Flow sensor 510 may be any type of device (e.g., ultrasonic detector,paddle-wheel sensor, pitot tube, drag-force flowmeter) configured tomeasure the flow rate or velocity using any applicable flow sensingmethod. In some embodiments, flow sensor 510 is a heated thermistor flowsensor that operates according to the principles of King's Law.According to King's Law, the heat transfer from a heated object exposedto a moving fluid is a function of the velocity of the fluid. King's Lawdevices have several features, including very high sensitivity at lowflow rates and measurement of the fluid temperature (which may be usefulfor fault detection and control purposes), although they have decreasedsensitivity at high flow rates.

In other embodiments, flow sensor 510 is a vortex-shedding flowmeterconfigured to determine the fluid flow rate by calculating the Strouhalnumber. The Strouhal number is a dimensionless value useful forcharacterizing oscillating flow dynamics. A vortex-shedding flowmetermeasures the flow rate via acoustic detection of vortices in fluidcaused when the fluid flows past a cylindrically-shaped obstruction. Thevibrating frequency of the vortex shedding is correlated to the flowvelocity. Vortex-shedding flowmeters have good sensitivity over a rangeof flow rates, although they require a minimum flow rate in order to beoperational.

Turning now to FIG. 6, a block diagram of another pressure disturbancerejection valve assembly 600 is shown, according to some embodiments.Valve assembly 600 may be used in HVAC system 100, waterside system 200,airside system 300, or BMS 400, as described with reference to FIGS.1-4. Valve assembly 600 may represent a more detailed version of valveassembly 500. For example, valve assembly 600 is shown to includeactuator 602, which may be identical or substantially similar toactuator 502 in valve assembly 500. Actuator 602 may be configured tooperate equipment 604. Equipment 604 may include any type of system ordevice that can be operated by an actuator (e.g., a valve, a damper). Inan exemplary embodiment, actuator 602 and equipment 604 (e.g., a valve)are packaged within a common integrated device chassis.

Actuator 602 is shown to include a processing circuit 606 communicablycoupled to motor 628. In some embodiments, motor 628 is a brushless DC(BLDC) motor. Processing circuit 606 is shown to include a processor608, memory 610, and a main actuator controller 632. Processor 608 canbe a general purpose or specific purpose processor, an applicationspecific integrated circuit (ASIC), one or more field programmable gatearrays (FPGAs), a group of processing components, or other suitableprocessing components. Processor 608 can be configured to executecomputer code or instructions stored in memory 610 or received fromother computer readable media (e.g., CDROM, network storage, a remoteserver, etc.).

Memory 610 may include one or more devices (e.g., memory units, memorydevices, storage devices, etc.) for storing data and/or computer codefor completing and/or facilitating the various processes described inthe present disclosure. Memory 610 may include random access memory(RAM), read-only memory (ROM), hard drive storage, temporary storage,non-volatile memory, flash memory, optical memory, or any other suitablememory for storing software objects and/or computer instructions. Memory610 may include database components, object code components, scriptcomponents, or any other type of information structure for supportingthe various activities and information structures described in thepresent disclosure. Memory 610 can be communicably connected toprocessor 608 via processing circuit 606 and may include computer codefor executing (e.g., by processor 608) one or more processes describedherein. When processor 608 executes instructions stored in memory 610,processor 608 generally configures actuator 602 (and more particularlyprocessing circuit 606) to complete such activities.

Main actuator controller 632 may be configured to receive externalcontrol data 616 (e.g., position setpoints, speed setpoints, etc.) fromcommunications circuit 612, position signals 624 from position sensors622, and flow signals 640 from flow sensors 638. Main actuatorcontroller 632 may be configured to determine the position of motor 628and/or drive device 630 based on position signals 624. In someembodiments, main actuator controller 632 receives data from additionalsources. For example, motor current sensor 618 may be configured tomeasure the electric current provided to motor 628. Motor current sensor618 may generate a feedback signal indicating the motor current 620 andmay provide this signal to main actuator controller 632 withinprocessing circuit 608.

Fault detection circuit 636 may be configured to utilize data receivedby the main actuator controller 632 (e.g., position signals 624, flowsignals 640) in order to detect fault conditions experienced by thevalve assembly 600. In some embodiments, the fault detection circuit 636stores various rules and data (e.g., error thresholds) related to thedetection of fault conditions. Further details are included below withreference to FIGS. 8-11. The fault detection circuit 636 may also beconfigured to perform various fault mitigation actions in response todetection of a fault condition. For example, upon detection of a faultcondition, the fault detection circuit 636 may transmit a faultnotification message to a supervisory controller via the communicationscircuit 612. Various fault mitigation actions are described in furtherdetail below with reference to FIG. 12.

Still referring to FIG. 6, processing circuit 608 may be configured tooutput a pulse width modulated (PWM) DC motor command 634 to control thespeed of the motor. Motor 628 may be configured to receive a three-phasePWM voltage output (e.g., phase A, phase B, phase C) from motor driveinverter 626. The duty cycle of the PWM voltage output may define therotational speed of motor 628 and may be determined by processingcircuit 606 (e.g., a microcontroller). Processing circuit 606 mayincrease the duty cycle of the PWM voltage output to increase the speedof motor 628 and may decrease the duty cycle of the PWM voltage outputto decrease the speed of motor 628.

Motor 628 may be coupled to drive device 630. Drive device 630 may be adrive mechanism, a hub, or other device configured to drive oreffectuate movement of a HVAC system component (e.g., equipment 604).For example, drive device may be configured to receive a shaft of adamper, a valve, or any other movable HVAC system component in order todrive (e.g., rotate) the shaft. In some embodiments, actuator 602includes a coupling device configured to aid in coupling drive device630 to the movable HVAC system component. For example, the couplingdevice may facilitate attaching drive device 630 to a valve or dampershaft.

Position sensors 622 may include Hall effect sensors, potentiometers,optical sensors, or other types of sensors configured to measure therotational position of the motor 628 and/or drive device 630. Positionsensors 622 may provide position signals 624 to processing circuit 606.Main actuator controller 632 may use position signals 624 to determinewhether to operate the motor 628. For example, main actuator controller632 may compare the current position of drive device 630 with a positionsetpoint received via external data input 616 and may operate the motor628 to achieve the position setpoint.

Actuator 602 is further shown to include a communications circuit 612.Communications circuit 612 may be a wired or wireless communicationslink and may use any of a variety of disparate communications protocols(e.g., BACnet, LON, WiFi, Bluetooth, NFC, TCP/IP, etc.). In someembodiments, communications circuit 612 is an integrated circuit, chip,or microcontroller unit (MCU) configured to bridge communicationsactuator 602 and external systems or devices. In some embodiments,communications circuit 612 is the Johnson Controls BACnet on a Chip(JBOC) product. For example, communications circuit 612 can be apre-certified BACnet communication module capable of communicating on abuilding automation and controls network (BACnet) using a master/slavetoken passing (MSTP) protocol. Communications circuit 612 can be addedto any existing product to enable BACnet communication with minimalsoftware and hardware design effort. In other words, communicationscircuit 612 provides a BACnet interface for the pressure disturbancerejection valve assembly 600. Further details regarding the JBOC productare disclosed in U.S. patent application Ser. No. 15/207,431 filed Jul.11, 2016, the entire disclosure of which is incorporated by referenceherein.

Communications circuit 612 may also be configured to support datacommunications within actuator 602. In some embodiments, communicationscircuit 612 may receive internal actuator data 614 from main actuatorcontroller 632. For example, internal actuator data 614 may include thesensed motor current 620, a measured or calculated motor torque, theactuator position or speed, configuration parameters, end stoplocations, stroke length parameters, commissioning data, equipment modeldata, firmware versions, software versions, time series data, acumulative number of stop/start commands, a total distance traveled, anamount of time required to open/close equipment 604 (e.g., a valve), orany other type of data used or stored internally within actuator 602. Insome embodiments, communications circuit 612 may transmit external data616 to main actuator controller 632. External data 616 may include, forexample, position setpoints, speed setpoints, control signals,configuration parameters, end stop locations, stroke length parameters,commissioning data, equipment model data, actuator firmware, actuatorsoftware, or any other type of data which can be used by actuator 602 tooperate the motor 628 and/or drive device 630.

In some embodiments, external data 616 is a DC voltage control signal.Actuator 602 can be a linear proportional actuator configured to controlthe position of drive device 630 according to the value of the DCvoltage received. For example, a minimum input voltage (e.g., 0.0 VDC)may correspond to a minimum rotational position of drive device 630(e.g., 0 degrees, −5 degrees, etc.), whereas a maximum input voltage(e.g., 10.0 VDC) may correspond to a maximum rotational position ofdrive device 630 (e.g., 90 degrees, 95 degrees, etc.). Input voltagesbetween the minimum and maximum input voltages may cause actuator 602 tomove drive device 630 into an intermediate position between the minimumrotational position and the maximum rotational position. In otherembodiments, actuator 602 can be a non-linear actuator or may usedifferent input voltage ranges or a different type of input controlsignal (e.g., AC voltage or current) to control the position and/orrotational speed of drive device 630.

In some embodiments, external data 616 is an AC voltage control signal.Communications circuit 612 may be configured to transmit an AC voltagesignal having a standard power line voltage (e.g., 120 VAC or 230 VAC at50/60 Hz). The frequency of the voltage signal can be modulated (e.g.,by main actuator controller 632) to adjust the rotational positionand/or speed of drive device 630. In some embodiments, actuator 602 usesthe voltage signal to power various components of actuator 602. Actuator602 may use the AC voltage signal received via communications circuit612 as a control signal, a source of electric power, or both. In someembodiments, the voltage signal is received from a power supply linethat provides actuator 602 with an AC voltage having a constant orsubstantially constant frequency (e.g., 120 VAC or 230 VAC at 50 Hz or60 Hz). Communications circuit 612 may include one or more dataconnections (separate from the power supply line) through which actuator602 receives control signals from a controller or another actuator(e.g., 0-10 VDC control signals).

Feedback Control System

Turning now to FIG. 7, a block diagram of an actuator device 702 withina feedback control system 700 is shown. In some embodiments, thefeedback control system 700 is a cascaded feedback control system. In acascaded control system, a primary controller (e.g., controller 704)generates a control signal that serves as the setpoint for a secondarycontroller (e.g., flow/velocity feedback controller 736). In someembodiments, the control path including the control signal generated bythe primary controller may be referred to as an “outer loop,” while thecontrol path including the secondary controller may be referred to as an“inner loop.” In some embodiments, cascaded control system 700 is acomponent or subsystem of HVAC system 100, waterside system 200, airsidesystem 300, or BMS 400, as described with reference to FIGS. 1-4.

Cascaded control system 700 may include, among other components,actuator device 702, controller 704, building zone 706, zone temperaturecontroller 724, and valve 746. In some embodiments, controller 704 is aprimary controller for the components of an HVAC system (e.g., HVACsystem 100) within the outer control loop of cascaded control system700. In other embodiments, controller 704 is a thermostat or a BMScontroller (e.g., for BMS 400). In still further embodiments, controller704 is a user device configured to run a building management application(e.g., a mobile phone, a tablet, a laptop). Controller 704 may receivedata from temperature sensor 708. Temperature sensor 708 may be any typeof sensor or device configured to measure an environmental condition(e.g., temperature) of a building zone 706. Building zone 706 may be anysubsection of a building (e.g., a room, a block of rooms, a floor).

Controller 704 is shown to include a digital filter 712, a wirelesscommunications interface 718, and a comparator 720. Measured zonetemperature data 710 from temperature sensor 708 may be received as aninput signal to digital filter 712. Digital filter 712 may be configuredto convert the measured zone temperature data 710 into a measured zonetemperature feedback signal 714 that may be provided as an input tocomparator 720. In some embodiments, digital filter 712 is a first orderlow pass filter. In other embodiments, digital filter 712 may be a lowpass filter of a different order or a different type of filter.

Controller 704 is further shown to include wireless communicationsinterface 718. In some embodiments, wireless communications interface718 may communicate data from controller 704 to communications interface752 of actuator device 702. In other embodiments, communicationsinterfaces 718 and 752 may communicate with other external systems ordevices. Communications via interface 718 may be direct (e.g., localwireless communications) or via a communications network (e.g., a WAN,the Internet, a cellular network). For example, interfaces 718 and 752may include a Wi-Fi transceiver for communicating via wirelesscommunications network. In another example, one or both interfaces 718and 752 may include cellular or mobile phone communicationstransceivers. In some embodiments, multiple controllers and smartactuator devices may communicate using a mesh topology. In otherembodiments, communications interfaces 718 and 752 may be configured totransmit smart actuator device data (e.g., a fault status, an actuatorand/or valve position) to an external network. In still furtherembodiments, communications interfaces 718 and 752 are connected via awired, rather than wireless, network.

Comparator 720 may be configured to compare the measured zonetemperature feedback signal 714 output from digital filter 712 with azone temperature setpoint value 716. Comparator 720 may then output atemperature error signal 722 that is received by zone temperaturecontroller 724. Comparator 720 may be a discrete electronics part orimplemented as part of controller 704. If comparator 720 determines thatthe zone temperature feedback signal 714 is higher than the zonetemperature setpoint value 716 (i.e., building zone 706 is hotter thanthe setpoint value), zone temperature controller 724 may output acontrol signal that causes actuator device 702 to modify the flow ratethrough water coil 750 such that cooling to building zone 706 isincreased. If comparator 720 determines that the zone temperaturefeedback signal 714 is lower than the zone temperature setpoint value716 (i.e., building zone 706 is cooler than the setpoint value), zonetemperature controller 724 may output a control signal that causesactuator device 702 to modify the flow rate through water coil 750 suchthat heating to building zone 706 is increased.

In various embodiments, zone temperature controller 724 is a patternrecognition adaptive controller (PRAC), a model recognition adaptivecontroller (MRAC), or another type of tuning or adaptive feedbackcontroller. Adaptive control is a control method in which a controllermay adapt to a controlled system with associated parameters which vary,or are initially uncertain. In some embodiments, zone temperaturecontroller 724 is similar or identical to the adaptive feedbackcontroller described in U.S. Pat. No. 8,825,185, granted on Sep. 2,2014, the entirety of which is herein incorporated by reference.

Still referring to FIG. 7, actuator device 702 is shown to include aflow/velocity span block 726, a comparator 730, a flow/velocity feedbackcontroller 736, a valve actuator 740, and a communications interface752. Zone temperature error 722 output from comparator 720 may betransmitted to actuator 702 via zone temperature controller 724.Flow/velocity span block 726 may be configured to enforce allowablemaximum and minimum flow range limits on the received zone temperatureerror 722. For example, a technician installing the components ofcascaded control system 700 or an administrator of HVAC system 100 mayinput a maximum and/or a minimum flow range limit for the flow/velocityspan block 726. In some embodiments, the flow range limits aretransmitted via mobile device (e.g., a smart phone, a table) and arereceived via communications interface 752 of actuator device 702. Inother embodiments, the flow range limits are transmitted to interface752 via wired network.

In other embodiments, flow limits may be calibrated on-site (e.g., by awater balancer) at the building location. For example, a water balancermay be used to manually adjust the position of valve 746 until a desiredmaximum and/or minimum flow rate is obtained, as measured by certifiedequipment. In some embodiments, these limits are subsequentlycommunicated to flow/velocity span block 726. The water balancingtechnique may be desirable when a high degree of accuracy in flow ratemeasurement is desired. In still further embodiments, logic withinactuator device 702 (e.g., flow/velocity feedback controller 736) mayprovide feedback to flow/velocity span block 726 to adjust the flow ratelimits based on historical operating data.

Comparator 730 may compare the flow rate/velocity setpoint 728 outputreceived from flow/velocity span block 726 to measured flowrate/velocity data. Measured flow rate velocity data may be receivedfrom flow rate sensor 748. Comparator 730 may be a discrete electronicspart or implemented as part of flow/velocity feedback controller 736. Insome embodiments, comparator 730 may output a flow rate/velocity errorsignal 734 to flow/velocity feedback controller 736. For example, ifcomparator 730 determines that flow rate/velocity setpoint 728 is higherthan measured flow rate/velocity 742, comparator 730 may generate a flowrate/velocity error signal 734 that causes flow/velocity feedbackcontroller 736 to operate valve actuator 740 to increase the flowrate/velocity through valve 746. Conversely, if comparator 730determines that flow rate/velocity setpoint 728 is lower than measuredflow rate/velocity 742, comparator 730 may generate a flow rate/velocityerror signal 734 that causes flow/velocity feedback controller 736 tooperate valve actuator 740 to decrease the flow rate/velocity throughvalve 746.

Flow/velocity feedback controller 736 is configured to receive a flowrate/velocity error signal 734 from comparator 730 and to output acommand signal to valve actuator 740 to drive the error signal to zero(i.e., to operate valve actuator 740 such that the measured flowrate/velocity 742 is equal to the flow rate/velocity setpoint 728).Similar to zone temperature controller 724, in various embodiments,flow/velocity feedback controller 736 is a proportional variabledeadband controller (PVDC), a pattern recognition adaptive controller(PRAC), a model recognition adaptive controller (MRAC), or another typeof tuning or adaptive feedback controller. In other embodiments,flow/velocity feedback controller 736 operates using state machine orproportional-integral-derivative (PID) logic. In some embodiments,flow/velocity feedback controller 736 is identical or substantiallysimilar to the main actuator controller 632 as described with referenceto FIG. 6.

Flow/velocity feedback controller 736 may be configured to output anactuator control signal (e.g., a DC signal, an AC signal) to valveactuator 740. In some embodiments, valve actuator 740 is identical orsubstantially similar to actuators 502 and 602 as described withreference to FIGS. 5 and 6. For example, valve actuator 740 may be alinear actuator (e.g., a linear proportional actuator), a non-linearactuator, a spring return actuator, or a non-spring return actuator.Valve actuator 740 may include a drive device coupled to valve 746 andconfigured to rotate a shaft of valve 746. In some embodiments, valve746 is identical or substantially similar to valves 504 and 604 asdescribed with reference to FIGS. 5 and 6. For example, in variousembodiments, valve 746 may be a 2-way or 3-way two position electricmotorized valve, a ball isolation valve, a floating point control valve,an adjustable flow control device, or a modulating control valve.

Still referring to FIG. 7, cascaded flow rate system is further shown toinclude a flow rate sensor 748. In some embodiments, flow rate sensor748 is identical or substantially similar to the flow rate sensors 510and 638 as described with reference to FIGS. 5 and 6. For example, invarious embodiments, flow rate sensor 748 may be a heated thermistorflow sensor or a vortex-shedding flowmeter. Flow rate sensor 748 may bedisposed downstream of valve 746 to measure the flow rate and/orvelocity of fluid exiting valve 746. In some embodiments, flow ratesensor 748 is configured to have high sensitivity to changes in flowrate or velocity and, at the same time, to reject pressure fluctuationswithin the system. In further embodiments, cascaded control systems maybe configured to reject fluctuations in system characteristics otherthan pressure. For example, these characteristics may include inletwater temperature, inlet air temperature, and airside mass flow. Oncecollected, measured flow rate and/or velocity data 742 from flow ratesensor 748 may be provided to comparator 730 of actuator device 702.

Fluid that passes through valve 746 may flow through water coil 750. Insome embodiments, valve 746 is used to modulate an amount of heating orcooling provided to the supply air for building zone 706. In variousembodiments, water coil 750 may be used to achieve zone setpointtemperature 716 for the supply air of building zone 706 or to maintainthe temperature of supply air for building zone 706 within a setpointtemperature range. The position of valve 746 may affect the amount ofheating or cooling provided to supply air via water coil 750 and maycorrelate with the amount of energy consumed to achieve a desired supplyair temperature.

Fault Detection and Diagnosis

Referring now to FIGS. 8-11, multiple state transition diagrams 800-1100illustrating the state transitions and transition conditions experiencedby a pressure disturbance rejection valve assembly during various faultconditions are shown, according to some embodiments. In someembodiments, the logic of state transition diagrams 800-1100 may beimplemented by one or more of the fault detection circuit 636 and mainactuator controller 632 of the actuator 602 depicted in FIG. 6, and theflow/velocity feedback controller 736 of the actuator 702 of FIG. 7. Forthe purposes of simplicity, state transition diagrams 800-1100 will bedescribed below exclusively with reference to actuator 602 of FIG. 6.

FIG. 8 depicts a state transition diagram 800 including logic configuredto detect a valve position fault. As shown, state transition diagram 800includes a normal state 802, a timing state 804, and a fault state 806.Under nominal conditions, the actuator 602 may operate in the normalstate 802. If the fault detection circuit 636 detects that thedifference between the current valve position and the valve commandposition is greater than a specified error value, condition 808 issatisfied and actuator 602 transitions from the normal state 802 to thetiming state 804. The timing state 804 may be utilized to ensure thatany detected faults are not attributable to transient conditions. Invarious embodiments, the specified error value used as the criterion todetect the valve position fault may be configured during the valveassembly manufacturing process. In other embodiments, the error valuemay be configurable by a user or technician.

If the fault detection circuit 636 detects that a delay period haselapsed and the actuator 602 is not experiencing a mere transient fault,condition 812 is satisfied and actuator 602 transitions from the timingstate 804 to the fault state 806. Similar to the error value, the delayperiod may be configured by the manufacturer or the end user. Actuator602 may operate in the fault state 806 indefinitely so long as thedifference between the current valve position and the valve commandposition is greater than the specified error value. While operating inthe fault state 806, the fault detection circuit 636 may perform variousfault mitigation actions, described in further detail below withreference to FIG. 12.

If the fault detection circuit 636 detects that the difference betweenthe current valve position and the valve command position is less thanor equal to the specified error value, either condition 810 issatisfied, and the actuator 602 transitions from the timing state 804 tothe normal state 802, or condition 814 is satisfied, and the actuator602 transitions from the fault state 806 to the normal state 802. Insome embodiments, the fault detection circuit 636 continually monitorsthe current valve position to determine whether the actuator 602 shouldremain in the fault state 806. In other embodiments, the fault detectioncircuit 636 monitors the current valve position at discrete intervals todetermine whether the actuator 602 should remain in the fault state 806.

Referring now to FIG. 9, a state transition diagram 900 including logicconfigured to detect a low flow valve fault is depicted, according tosome embodiments. As shown, state transition diagram 900 includes avalve position no fault state 902 and a valve position fault state 904.If the fault detection circuit 636 detects a valve position fault,condition 906 is satisfied and the actuator 602 transitions from thevalve position no fault state 902 to the valve position fault state 904.In some embodiments, the valve position fault state 904 is identical tofault state 806, described above with reference to FIG. 8. Conversely,if the fault detection circuit 636 detects no valve position fault,condition 908 is satisfied and the actuator 602 transitions from thevalve position fault state 904 to the valve no fault state 902.

Within the valve position no fault state 902, the fault detectioncircuit 636 transitions between a normal state 910, a timing state 912,and a fault state 914. If the fault detection circuit 636 detects thatthe valve command position is the valve fully open position (i.e., 100%open) and the measured flow rate is less than a flow rate setpointvalue, condition 916 is satisfied and the actuator 602 transitions fromthe normal state 910 to the timing state 912. While operating in thetiming state 912, if the fault detection circuit 636 determines thateither 1) the valve command position is less than fully open or 2) themeasured flow rate is greater than or equal to the flow rate setpointvalue, condition 918 is satisfied and the actuator 602 reverts from thetiming state 912 to the normal state 910. However, if the faultdetection circuit 636 detects that a delay period has elapsed, condition920 is satisfied and the actuator 602 transitions from the timing state912 to the fault state 914.

Actuator 602 may operate in the fault state 914 indefinitely so long asthe valve command position is the valve fully open position and themeasured flow rate is less than a flow rate setpoint value. However, ifthe fault detection circuit 636 detects that the actuator 602 is nolonger experiencing a low flow valve fault condition (i.e., either 1)the valve command position is less than fully open or 2) the measuredflow rate is greater than or equal to the flow rate setpoint value),condition 922 is satisfied, and the actuator 602 reverts to the normalstate 910 from the fault state 914.

Turning now to FIG. 10, a state transition diagram 1000 including logicconfigured to detect a no flow valve fault is depicted, according tosome embodiments. As shown, state transition diagram 1000 includes avalve position no fault state 1002 and a valve position fault state1004. Similar to state transition diagrams 800 and 900 described above,if the fault detection circuit 636 detects a valve position fault,condition 1006 is satisfied and the actuator 602 transitions from thevalve position no fault state 1002 to the valve position fault state1004. Once operating in the valve position fault state 1004, if thefault detection circuit 636 detects no valve position fault, condition1008 is satisfied and the actuator 602 reverts to the valve position nofault state 1002 from the valve position fault state 1004.

Within the valve position no fault state 1002, the fault detectioncircuit 636 transitions between a normal state 1010, a timing state1012, and a fault state 1014. If the fault detection circuit 636 detectsthat the valve command position is greater than a minimum open positionand the measured flow rate is less than a minimum rated flow rate,condition 1016 is satisfied and the actuator 602 transitions from thenormal state 1010 to the timing state 1012. While operating in thetiming state 1012, if the fault detection circuit 636 determines thateither 1) the valve command position is less than or equal to theminimum open position or 2) the measured flow rate is greater than orequal to the minimum rated flow rate, condition 1018 is satisfied andthe actuator 602 transitions from the timing state 1012 to the normalstate 1010. However, if the fault detection circuit 636 detects that adelay period has elapsed, condition 1020 is satisfied and the actuator602 transitions from the timing state 1012 to the fault state 1014.

Actuator 602 may operate in the fault state 1014 indefinitely so long asthe valve command position is greater than a minimum open position andthe measured flow rate is less than a minimum rated flow rate. However,if the fault detection circuit 636 detects that the actuator 602 is nolonger experiencing a no flow valve fault condition (i.e., either 1) thevalve command position is less than or equal to the minimum openposition or 2) the measured flow rate is greater than or equal to theminimum rated flow rate), condition 1022 is satisfied, and the actuator602 reverts to the normal state 1010 from the fault state 1014.

Referring now to FIG. 11, a state transition diagram 1100 includinglogic configured to detect a leaky valve fault is depicted, according tosome embodiments. As shown, similar to diagrams 900 and 1000 describedabove, state transition diagram 1100 includes a valve position no faultstate 1102 and a valve position fault state 1104. Actuator 602 maytransition between states 1102 and 1104 based on the satisfaction ofconditions 1106 and 1108, as detected by fault detection circuit 636.

Within the valve position no fault state 1102, the fault detectioncircuit 636 transitions between a normal state 1110, a timing state1112, and a fault state 1114. If the fault detection circuit 636 detectsthat the valve command position is fully closed (i.e., 0% open) and themeasured flow rate exceeds a leaky flow rate threshold, condition 1116is satisfied and the actuator 602 transitions from the normal state 1110to the timing state 1112. While operating in the timing state 1112, ifthe fault detection circuit 636 determines that either 1) the valvecommand position is greater than or equal to a minimum open position or2) the measured flow rate is less than or equal to the leaky flow ratethreshold, condition 1118 is satisfied and the actuator 602 transitionsfrom the timing state 1112 to the normal state 1110. However, if thefault detection circuit 636 detects that a delay period has elapsed,condition 1120 is satisfied and the actuator 602 transitions from thetiming state 1112 to the fault state 1114.

Actuator 602 may operate in the fault state 1114 indefinitely so long asthe valve command position is fully closed and the measured flow rateexceeds a leaky flow rate threshold. However, if the fault detectioncircuit 636 detects that the actuator 602 is no longer experiencing aleaky valve fault condition (i.e., either 1) the valve command positionis greater than or equal to a minimum open position or 2) the measuredflow rate is less than or equal to the leaky flow rate threshold),condition 1122 is satisfied, and the actuator 602 reverts to the normalstate 1110 from the fault state 1114.

Turning now to FIG. 12, a flow diagram of a process 1200 for operating apressure disturbance rejection valve assembly is shown, according to anexemplary embodiment. In some embodiments, process 1200 may be performedby at least in part by the fault detection circuit 636 of the mainactuator controller 632, described above with reference to FIG. 6.Process 1200 is shown to commence with step 1202, in which the mainactuator controller 632 determines an actuator position setpoint. Insome embodiments, determination of the actuator position setpoint isperformed by a controller employing a PVDC control scheme. At step 1204,the main actuator controller 632 operates the motor 628 and the drivedevice 630 to drive the drive device 632 and the valve 604 to theposition setpoint.

Process 1200 continues with step 1206, in which the fault detectioncircuit 636 detects a fault condition. In some embodiments, detecting afault condition involves applying the logic of state transition diagrams800-1100, described above with reference to FIGS. 8-11, and detecting atransition from a timing state into a fault state. Process 1200concludes with step 1208, in which the fault detection circuit 636performs a fault mitigation action. In some embodiments, the faultmitigation action includes any or all of transmitting a faultnotification message to a technician or system administrator via textmessage or electronic mail, activating a system alarm, logging an entryin a system log, and illuminating a fault indicator light. In otherembodiments, the fault mitigation action includes instructing asupervisory device (e.g., an external controller) to operate theactuator 602 in a fault tolerant control (FTC) mode.

Configuration of Exemplary Embodiments

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible. For example, the position of elements may bereversed or otherwise varied and the nature or number of discreteelements or positions may be altered or varied. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure. The order or sequence of any process or method stepsmay be varied or re-sequenced according to alternative embodiments.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions and arrangement of the exemplaryembodiments without departing from the scope of the present disclosure.

The present disclosure contemplates methods, systems and programproducts on any machine-readable media for accomplishing variousoperations. The embodiments of the present disclosure may be implementedusing existing computer processors, or by a special purpose computerprocessor for an appropriate system, incorporated for this or anotherpurpose, or by a hardwired system. Embodiments within the scope of thepresent disclosure include program products comprising machine-readablemedia for carrying or having machine-executable instructions or datastructures stored thereon. Such machine-readable media can be anyavailable media that can be accessed by a general purpose or specialpurpose computer or other machine with a processor. By way of example,such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROMor other optical disk storage, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to carry or storedesired program code in the form of machine-executable instructions ordata structures and which can be accessed by a general purpose orspecial purpose computer or other machine with a processor. Combinationsof the above are also included within the scope of machine-readablemedia. Machine-executable instructions include, for example,instructions and data which cause a general purpose computer, specialpurpose computer, or special purpose processing machines to perform acertain function or group of functions.

Although the figures show a specific order of method steps, the order ofthe steps may differ from what is depicted. Also two or more steps maybe performed concurrently or with partial concurrence. Such variationwill depend on the software and hardware systems chosen and on designerchoice. All such variations are within the scope of the disclosure.Likewise, software implementations could be accomplished with standardprogramming techniques with rule based logic and other logic toaccomplish the various connection steps, processing steps, comparisonsteps and decision steps.

What is claimed is:
 1. A pressure disturbance rejection valve assemblyconfigured to modify an environmental condition of a building, the valveassembly comprising: a valve configured to regulate a flow rate of afluid through a conduit; a flow rate sensor configured to measure theflow rate of the fluid through the conduit and provide a flow ratemeasurement indicating the flow rate of the fluid through the conduit;an actuator comprising: a motor; a drive device configured to be drivenby the motor and coupled to the valve for driving the valve within arange of positions; a position sensor configured to measure a rotationalposition of the drive device and provide a rotational positionmeasurement indicating the rotational position of the drive device; acommunications mechanism configured to receive a flow rate setpoint froman external control device of an outer control loop; and a processingcircuit coupled to the motor, the communications mechanism, the positionsensor, and the flow rate sensor, the processing circuit configured to:determine an actuator position setpoint using a feedback controlmechanism based on the flow rate setpoint and the flow rate measurement;operate the motor to drive the drive device to the actuator positionsetpoint; detect a fault condition based at least in part on theactuator position setpoint and a comparison of the flow rate setpointand the flow rate measurement; and perform a fault mitigation action inresponse to detection of the fault condition.
 2. The valve assembly ofclaim 1, wherein the communications mechanism is configured to receivethe flow rate setpoint as at least one of an analog input signal or adigital input signal.
 3. The valve assembly of claim 1, wherein thefeedback control mechanism is a cascaded feedback control mechanism. 4.The valve assembly of claim 1, wherein the fault condition is a positionfault comprising a difference between the actuator position setpoint andthe rotational position measurement exceeding a position error value. 5.The valve assembly of claim 1, wherein the fault condition is a low flowfault.
 6. The valve assembly of claim 5, wherein the low flow faultcomprises the flow rate measurement being less than a flow rate setpointvalue when the rotational position measurement indicates that the valveis in a fully open position.
 7. The valve assembly of claim 1, whereinthe fault condition is a no flow fault.
 8. The valve assembly of claim7, wherein the no flow fault comprises the flow rate measurement beingless than a minimum rated flow rate value when the rotational positionmeasurement indicates that the valve exceeds a minimum open position. 9.The valve assembly of claim 1, wherein the fault condition is a leakyvalve fault.
 10. The valve assembly of claim 9, wherein the leaky valvefault comprises the flow rate measurement exceeding a leaky flow ratevalue when the rotational position measurement indicates that the valveis in a fully closed position.
 11. The valve assembly of claim 1,wherein the fault mitigation action comprises at least one oftransmitting a fault notification message, activating a system alarm,logging an entry in a system log, illuminating a fault indicator light,or operating in a fault tolerant control mode.
 12. A method forcontrolling a pressure disturbance rejection valve assembly in an HVACsystem, the method comprising: determining an actuator position setpointof an actuator based on a flow rate setpoint and a flow ratemeasurement; driving the actuator to the actuator position setpoint,wherein the actuator is coupled to a valve in order to drive the valvewithin a range of positions; measuring a flow rate of fluid through thevalve; detecting a fault condition based at least in part on theactuator position setpoint and a comparison of the flow rate setpointand the flow rate measurement; and performing a fault mitigation actionin response to detection of the fault condition.
 13. The method of claim12, wherein the fault condition is a position fault comprising adifference between the actuator position setpoint and a rotationalposition measurement exceeding a position error value.
 14. The method ofclaim 12, wherein the fault condition is a low flow fault.
 15. Themethod of claim 14, wherein the low flow fault comprises the flow ratemeasurement being less than a flow rate setpoint value when a rotationalposition measurement indicates that the valve is in a fully openposition.
 16. The method of claim 12, wherein the fault condition is ano flow fault.
 17. The method of claim 16, wherein the no flow faultcomprises the flow rate measurement being less than a minimum rated flowrate value when a rotational position measurement indicates that thevalve exceeds a minimum open position.
 18. The method of claim 12,wherein the fault condition is a leaky valve fault.
 19. The method ofclaim 18, wherein the leaky valve fault comprises the flow ratemeasurement exceeding a leaky flow rate value when a rotational positionmeasurement indicates that the valve is in a fully closed position. 20.An actuator, comprising: a motor; a drive device configured to be drivenby the motor; a position sensor configured to measure a rotationalposition of the drive device and provide a rotational positionmeasurement indicating the rotational position of the drive device; acommunications mechanism configured to receive a flow rate setpoint froman external control device of an outer control loop; and a processingcircuit coupled to the motor, the communications mechanism, and theposition sensor, the processing circuit configured to: determine anactuator position setpoint using a feedback control mechanism based onthe flow rate setpoint and a flow rate measurement from a flow sensor;operate the motor to drive the drive device to the actuator positionsetpoint; detect a fault condition based at least in part on theactuator position setpoint and a comparison of the flow rate setpointand the flow rate measurement; transition the actuator to a fault statebased on determining the fault condition exists for at least a thresholdperiod of time; and perform a fault mitigation action in response totransitioning the actuator to the fault state.